This invention relates to the field of optical assemblies, and more particularly to a monolithic optical assembly for use in an interferometer.
Interferometers are old in the art, with Michelson interferometers having been first designed over 100 years ago.
An interferometer is an optical assembly used to measure radiation spectra, with the interferometer producing an interference pattern between two beams of light that traverse different paths. An interferometer divides a beam of radiation emanating from a radiation source through use of a beamsplitter inclined at a 45.degree. angle to two reflecting assemblies whose optical paths are at 90 degrees to each other. One of the reflecting assemblies is fixed, while the other is movable along the radiation's path, so as to introduce the path difference, thereby creating the interference pattern which is read by a detector after the divided beam of radiation is recombined through reflection off of the two reflecting assemblies. The variation in the intensity of the beams passing to the detector is a function of the path difference, and ultimately yields the spectral information in a Fourier transform spectrometer.
In practice, interferometers are used for the above discussed spectrometry, and for accurate distance measuring and equipment calibrations.
The prior art optical assemblies used in the construction of standard Michelson interferometers, and other type interferometers, have consisted primarily of structures having parts which are in need of high accuracy alignment. For example, the arrangement of the two reflecting assemblies and the beamsplitter must be highly accurate in the perpendicular and 45 degree arrangements in order to avoid errors introduced due to any such misalignment. The trouble with these prior art interferometers and optical assemblies results from the cost involved in meticulously aligning the optical pieces, and the subsequent cost of maintaining the alignment of those pieces after shocks and vibrations cause them to be misaligned.
A further disadvantage in the prior art optical assemblies and interferometers results from the physical need of replacing beamsplitters with different beamsplitters depending upon the radiation source used in a particular measurement or experiment. Specifically, a typical beamsplitter is useful for only one particular wavelength spectrum section of a source of radiation, or alternatively, a very small range of radiation wavelength spectrum sections, and it is therefore necessary to have multiple interferometers, each having different beamsplitters, or to constantly need to replace a beamsplitter in a single interferometer, so that the interferometer can be used for other applications.
Yet another disadvantage of the prior art optical assemblies and interferometers, is that they are constructed to only allow for use with single wavelength light sources. Specifically, in order to yield the spectral information resulting from use of a Fourier transform spectrometer ("fringes"), a light beam of only one wavelength (such as, laser light) is required to be used in all prior art interferometer devises.
Accordingly, it would be desirable to provide an optical assembly, with and without a retroreflector/beamsplitter combination, that provides high accuracy measurements in a unit which is monolithic in construction, so that field calibrations and maintenance of the optical components of the assembly are not required after shocks, vibrations, or due to temperature changes.
It would also be desirable to provide an optical assembly which is monolithically constructed and which forms the major alignment components of an interferometer, so as to facilitate easy and cost effective maintenance and replacement of the optical assembly within a single interferometer for use with different intensity radiations, which optical assembly is not subject to misalignment from shocks, vibrations, or temperature changes due to the monolithic structure of the assembly. It would be further desirable to provide an optical assembly which allows for use of multiple wavelength light sources to achieve a "fringe" result in a spectrometry application.